The Organic Chemistry of the Charophytes Chara and Lamprothamnium and their Degradation Products

Charophytes (stoneworts) have a fossil record since the late Silurian, and are therefore especially interesting from a biogeochemical point of view. They are commonly abundant in many modern and ancient non-marine lakes, and are among the closest living relatives to the higher plants. Charophytes possess highly specialised reproductive organs producing oospores (zygote and surrounding organic walls), which in some taxa are able to precipitate a calcareous shell (egg case) called a gyrogonite. The latter can easily fossilise, while the oospores usually decay, although they are common in more recent sediments. However, our knowledge of charophyte and oospore organic chemistry is still very fragmentary but is central to our understanding of charophyte biomarkers and land plant evolution. The main aim of this project is to determine the organic compounds present in charophytes in order to assess their potential as specific biomarkers. Furthermore, by studying both extant charophytes and their degradation products in recent sediments, we can evaluate whether particular compounds survive transport and erosion and can be potential biomarkers.